I have a WEBM file that I'd like to convert to MP4. (It's a long story but I produced the original video and converted it to webm for the web but have lost the original file. WEBM won't play on my local media server (WDTV) so I'd like to convert the webm file back to MP4).

I've tried Handbrake, VLC and AVIDEMUX. They all convert the file but I lose the audio in the conversion.